Sizing composition comprising a hydrophobic cellulose-reactive sizing agent and a cationic polymer

ABSTRACT

Disclosed is a sizing composition in the form of an aqueous emulsion comprising a hydrophobic cellulose-reactive sizing agent, such as a ketene dimer, and a cationic polymer selected from the group consisting of (1) a cationic polymer obtained by reacting an epihalohydrin with a condensate derived by condensing dicyandiamide or cyanamide with bis-aminopropylpiperazine and (2) a cationic polymer obtained by condensing an epihalohydrin with bis-aminopropylpiperazine. The cationic polymer is a sizing accelerator for the sizing agent.

This is a division of application Ser. No. 932,103, filed Aug. 9, 1978U.S. Pat. No. 4,243,481.

This invention relates to the use of certain cationic polymers in theproduction of sized paper and sized paperboard.

In particular, this invention relates to the manufacture of sized paperand sized paperboard wherein the sizing agent employed is a hydrophobiccellulose reactive sizing agent such as a ketene dimer sizing agent andthere is employed in combination therewith, as sizing accelerators,certain cationic polymers to provide substantially higheroff-the-machine sizing than when the cellulose reactive sizing agent isused alone.

U.S. Pat. No. 3,840,486 discloses water-soluble, thermosettable resinouscompositions derived by reaction of dicyandiamide, an ammonium salt,formaldehyde, and an acid salt of a water-soluble aminopolyamide such asthe water-soluble aminopolyamide derived by reaction of adiptic acid anddiethylenetriamine. The resinous compositions of U.S. Pat. No. 3,840,486accelerate the sizing imparted to paper by cellulose reactive sizingagents such as ketene dimers, acid anhydrides, and organic isocyanates.By employing the resinous compositions of U.S. Pat. No. 3,840,486 incombination with the above sizing agents for paper, higheroff-the-machine sizing is provided than when using equivalent amounts ofthe sizing agent alone.

United Kingdom patent specification No. 1,373,788 discloses the use ofdicyandiamide-formaldehyde condensates as sizing accelerators for ketenedimer sizing agents.

U.S. Pat. No. 3,409,500 discloses a process for the manufacture of sizedpaper which comprises separately adding an aqueous anionic dispersion ofhydrophobic organic cellulose-reactive paper sizing carboxylic anhydrideparticles to an aqueous suspension of cellulose papermaking fibers and awater-soluble cellulose-substantive cationic polyamine having amolecular weight in excess of 1,000, the amount of said polyamine beingat least sufficient to deposit said anhydride particles on said fibersand to accelerate the rate at which said anhydride develops its sizingproperties on cellulose fibers at 190° F.-250° F., sheeting saidsuspension to form a water-laid web, and drying said web at atemperature between 190° F. and 250° F.

In U.S. Pat. No. 3,409,500, at column 3, lines 61-70, it is stated thatamong the most efficient cationic polymers are the adipicacid-polyalkylenepolyamide-epichlorohydrin polymers, prepared bycondensing adipic acid with a polyalkylene-polyamine thereby forming apolyamidepolyamine, and reacting this polymer with epichlorohydrin.Methods for the preparation of agents of this type are disclosed in U.S.Pat. Nos. 2,926,116, 2,926,154 and 3,329,657.

The cationic polymers of U.S. Pat. Nos. 2,926,116 and 2,926,154 aredisclosed in U.S. Pat. No. 3,483,077 as being useful retention aids forketene dimer sizing agents whereby sizing is improved as compared tocationic starch retention aid.

U.S. Pat. No. 3,575,796 discloses a method for the sizing of paper andpaperboard products which comprises intimately dispersing within theaqueous pulp slurry, or applying to a prepared paper web, an aqueousemulsion of an N-substituted aziridine compound which is prepared bymeans of the reaction between a carbonyl-substituted, alpha,beta-ethylenically unsaturated compound such as distearyl maleate and analkyleneimine such as ethyleneimine. The sizing agent can be uniformlydispersed with a cationic emulsifier, such as a cationic starch, forbetter retention on the fibers. Column 4, lines 1-44 of U.S. Pat. No.3,575,796 discloses other cationic agents for use in aiding in theretention of the sizing agents of the invention among which are cationicthermosetting resins such as the reaction products of dibasic acids,polyalkylenepolyamines and epihalohydrins. It is stated also at column4, lines 45-62, that the cationic agents are also useful as emulsifiersfor the sizing agent.

U.S. Pat. No. 3,666,512 discloses compositions comprising hydrophobiccellulose-reactive paper-sizing carboxylic acid anhydrides and acatalyst which accelerates the rate at which the anhydride develops itssizing properties when deposited on cellulose from aqueous medium andheated. The catalyst or promoter for the anhydride size is awater-soluble cationic salt of a cellulose-substantive water-solublepolyamine. Suitable cationic agents are set forth in the table in column7 of the patent. Among the cationic agents is anamonopolyamide--epichlorohydrin resin, the aminopolyamide being derivedfrom diethylenetriamine and adipic acid.

Canadian Pat. No. 873,777 discloses a method for improving the wetstrength, dry strength, and resistance to penetration by liquids ofunsized paper comprising imbibing the paper with an amine oxide capableof swelling the paper fibers and a ketene dimer paper sizing agent,heating the paper to swell the paper fibers and removing the amine oxidefrom the paper.

U.S. Pat. No. 3,046,186 relates to the manufacture of sized paper by thebeater-addition process wherein an aqueous cationic dispersion of ahydrophobic ketene dimer is added to an aqueous suspension of cellulosicfibers. The sized paper is manufactured by forming an aqueous suspensionof cellulose papermaking fibers and adding thereto an emulsion of ahydrophobic ketene dimer in an aqueous medium containing a cationicdispersing agent which may be a monomeric or high molecular weighthydrophilic or water-soluble basic nitrogenous surface-active agent. Thedispersing agents are set forth in columns 3 and 4 of U.S. Pat. No.3,046,186.

U.S. Pat. No. 3,006,806 discloses the conjoint use of an organiccationic polymer with a ketene dimer in the sizing of paper. Cationicpolymers disclosed are melamine-formaldehyde resins (as described inU.S. Pat. No. 2,345,543 to Wohnsiedler and Thomas and U.S. Pat. No.2,559,220 to Maxwell and Lanes); urea-formaldehyde resins (as describedin U.S. Pat. No. 2,657,132 to Daniel, Landes and Suen); cationic cornstarch; guanidine-formaldehyde resins (U.S. Pat. No. 2,745,744 toWeidner and Dunlap); alkylenepolyamine-halohydrin resins (as describedin U.S. Pat. No. 2,601,597 to Daniel, Wilson and Landes); and cationicurea-formaldehyde resins (as described in British Pat. Nos. 675,477 and677,184).

U.S. Pat. No. 3,084,092 relates to paper manufactured by the conjointuse of an amino resin and a hydrophobic organic isocyanate. Amino resinsdisclosed in U.S. Pat. No. 3,084,092 are polyfunctional halohydrinresins of Daniel et al, U.S. Pat. No. 2,595,935; thedicyandiamide-formaldehyde-amine polymers of Dudley et al, U.S. Pat. No.2,596,014; the urea-monosubstituted urea resins of Schiller et al, U.S.Pat. No. 2,698,787; the polyamine-polyamide linear polymers of House etal, U.S. Pat. No. 2,729,560; the polymers formed by copolymerizingacrylamide and acrylic acid in 9:1 molar ratio; the sulfonateddimethylolurea resins of U.S. Pat. No. 2,582,840; and the aminosulfuricacid-melamine-formaldehyde resins of U.S. Pat. No. 2,688,607.

U.S. Pat. No. 3,248,353 relates to water-soluble cationic-substantivechemo-stable polymers of crosslinked long chain configuration useful asretention aids in the manufacture of paper. The polymers are prepared bysubstantially completely reacting to a point short of gelationepichlorohydrin with a major proportion of a water-soluble bifunctionalamine as chain-forming component and a minor proportion of awater-soluble polyfunctional amine having a functionality greater than 2as component forming secondary amine linkages in said chain, the ratioof the functionality of the epichlorohydrin to the total functionalityof said amines being substantially 1:1. Bifunctional amines includemethylamine, ethylamine, ethanolamine, propylamine,N,N'-dimethylethylenediamine, piperazine, and aniline (see column 2,lines 8-16). Polyfunctional amines are disclosed at column 2, lines17-25 and lines 32-38 and include amines such as ammonia,ethylenediamine, N-methylethylenediamine, diethylenetriamine,tetraethylenepentamine, p-phenylenediamine, p,p'-bisaniline, and1,3-diamino-2-propanol. The polymers are useful as retention aids forhigher fatty acid isocyanates, the higher fatty acid ketene dimers andthe higher fatty acid anhydrides (see column 3, lines 18-51).

According to the present invention there are provided certain cationicpolymers that are adapted particularly as sizing accelerators for usewith hydrophobic cellulose reactive sizing agents, such as ketenedimers, acid anhydrides, and organic isocyanates. The cationic polymersused in this invention increase the rate of sizing of the hydrophobiccellulose reactive sizing agents.

According to a further aspect of the invention there are provided novelsizing compositions for cellulose fibers comprising at least onehydrophobic cellulose reactive sizing agent and at least one cationicpolymer (sizing accelerator) as disclosed.

The preferred sizing compositions will be aqueous emulsions comprised ofthe cellulose reactive sizing agent, at least one emulsifier, and, as asizing accelerator, at least one of the cationic polymers. The term"emulsion" is used herein, as is customary in the art, to means either adispersion of the liquid-in-liquid type or of the solid-in-liquid type.

Aqueous emulsions of hydrophobic cellulose reactive sizing agents areknown in the art and are commercially available. To prepare the novelsizing compositions of this invention there is thoroughly admixed withthe emulsion an amount of cationic polymer sufficient to increase thesizing action of the sizing agent. It has been determined that from 0.25part to 3 parts by weight of the cationic polymer for each part byweight of the hydrophobic cellulose reactive sizing agent present in theemulsion provides good results.

Thus, the novel sizing compositions of this invention are aqueousemulsions that consist essentially of a hydrophobic cellulose reactivesizing agent, such as a ketene dimer, at least one emulsifier, and, assizing accelerator, at least one of the cationic polymers. The amount ofemulsifier(s) employed will be that sufficient to obtain and maintain anemulsion that is stable for a prolonged period of time and is within theskill of the art.

Emulsifier employed can be chosen from emulsifiers conventionallyemployed in the production of emulsions of cellulose reactive sizingagents. Such emulsifiers are well known in the art and include catonicstarches that are water-soluble starches carrying sufficient cationicamino groups, quaternary ammonium, or other cationic groups to renderthe starch, as a whole, cellulose-substantive. An example of such acationic starch is the cationic amine modified starch described inUnited Kingdom Patent Specification No. 903,416.

Another emulsifier that can be used is a water-soluble cationicthermosetting resin obtained by reacting epichlorohydrin with awater-soluble aminopolyamide formed from a dicarboxylic acid and apolyalkylene polyamine. Resins of this type are described in UnitedKingdom Patent Specification No. 865,727.

Cationic polymers useful as size accelerators are set forth below.

Cationic polymer (1) is a nitrogen-containing polymer obtained by firstcondensing bis-aminopropylpiperazine with dicyandiamide or cyanamide.The condensation reaction forms a low molecular weight polymer which isthen reacted with an epihalohydrin, such as epichlorohydrin.

Cationic polymer (1) is prepared in two stages. First, a prepolymercondensate is prepared by the condensation of bisaminopropylpiperazine(BAPP) and dicyandiamide in a mole ratio of BAPP to dicyandiamide offrom about 0.5:1 to 1:0.5. The preferred mole ratio is 1:1. Thereactants are admixed and heated at a temperature of from about150°-220° C. for from 1/2 hour to 4 hours, time varying inversely withtemperature. Ammonia, NH₃, is evolved during reaction and reaction isessentially complete when NH₃ ceases to be evolved. The prepolymer, inaqueous media, is then reacted with an epihalohydrin. Reaction withepihalohydrin is carried out at elevated temperature, preferably at atemperature of 50° C. to 80° C., until the reaction product has aviscosity, as measured on the Gardner-Holdt scale, of F to S. The amountof epihalohydrin used can be from 0.3 mole to 2 moles, preferably 1 moleto 1.5 moles, for each mole of amine nitrogen present in the prepolymercondensate. If cyanamide is used instead of dicyandiamide, moles ofcyanamide used will be twice the mole(s) of dicyandiamide.

In the examples that follow, all parts and percentages are by weightunless otherwise specified.

The following example is illustrative of the preparation of cationicpolymer (1).

EXAMPLE 1

To a 1-liter, 3-necked round-bottom flask equipped with a mechanicalstirrer, heating mantle, thermowatch temperature controller, and areflux condenser attached to a water trap were charged 200 g. (1 mole)of bis-aminopropylpiperazine and 84 g. (1 mole) dicyandiamide. Heatingwas started and continued to 160° C. with the evolution of ammonia. Themixture was held at 160° C. for 3 hours during which time more than 1mole of ammonia was collected and then the reaction was quenched by theaddition of 284 g. of distilled water giving an aqueous dispersion of44.4% total solids. To a 500 ml., 3-necked round-bottom flask containinga large fourth hole suitable for the insertion of pH electrodes tomonitor the reaction was attached a mechanical stirrer, reflux condenserand a Spurlin-Spence viscometer (essentially a fine bore tube with 5 ml.reservoir which is filled by suction and the time needed to pass througha fixed distance is measured). This reaction vessel was charged with 113g. (50 g. prepolymer solids) of the aqueous solution of the condensationprepolymer above prepared (equal to 0.4 amine equivalents) and 87 g. ofdistilled water in order to dilute the material to 25% solids. Then 46g. (0.5 mole) of epichlorohydrin was added. The initial reaction pH was12.1. There was an exothermic reaction which carried the temperature to60° C. and then heat was applied to maintain the temperature at 70° C.The viscosity began to increase 45 minutes after the epichlorohydrinaddition when the pH was 7.0. The reaction mass was heated another 45minutes during which time the viscosity increased to 15 seconds on theSpurlin-Spence viscometer (equivalent to a Gardner-Holdt viscosity of N)and the reaction was quenched by the addition of 234 g. of distilledwater and 14.4 g. of formic acid which lowered the pH of the product to4.0. The total solids was 24.0%.

Cationic polymer (2) is a nitrogen-containing polymer obtained bycondensing an alkylenediamine with an epihalohydrin, such asepichlorohydrin, in a mole ratio alkylenediamine to epihalohydrin of2:1. The product of this reaction is reacted with dicyandiamide orcyanamide to produce a low molecular weight polymer which is thenreacted with an epihalohydrin, such as epichlorohydrin. Examples ofalkylenediamines that can be used in the preparation of this cationicpolymer (2) are ethylenediamine, propylenediamine, andhexamethylenediamine. Mixtures of two or more alkylenediamines can beused if desired.

Cationic polymer (2) is produced in three stages. First, thealkylenediamine is reacted with an epihalohydrin in a mole ratio of 2 to1 at a temperature of 50°-80° C., over a period of 1 hour to 3 hours(time varies inversely with temperature) to provide a reaction product.This reaction product is then reacted with dicyandiamide at atemperature of 150°-220° C. for from 1/2 hour to 4 hours, time varyinginversely with temperature. The amount of dicyandiamide employed will befrom 1 mole to 2 moles for each mole of epichlorohydrin used in reactionwith the alkylenepolyamine, with 1 mole being preferred. This reactionproduct is then reacted with epihalohydrin in an amount of 2 to 2.5moles for each mole of epihalohydrin used in reaction with thealkylenediamine at a temperature of 25°-70° C. for a period of time of 1hour to 4 hours (time varies inversely with temperature). If cyanamideis used in place of dicyandiamide, moles of cyanamide used will be twicethe mole(s) of dicyandiamide.

The following example is illustrative of the preparation of cationicpolymer (2).

EXAMPLE 2

To a 500 ml. round-bottom, 3-necked flask equipped with a heatingmantle, thermowatch, mechanical stirrer and reflux condenser connectedto a water trap was added 120 g. ethylenediamine (2 moles). This washeated to 50° C. and 92 g. epichlorohydrin (1 mole) was added dropwiseover a 2 hour period. The temperature was allowed to rise to 60° C.,then increased to 80° C. by the application of heat. Dicyandiamide (84grams-1 mole) was then added to the contents of the flask. The reactionmixture was heated to 160° C. and maintained at this temperature for twohours. About 1.8 moles of NH₃ was evolved during the condensationreaction. 300 ml. water was added to provide a reaction mass containing48% solids. 104 g. of the 48% solids reaction mass (50 g. solids) wasdiluted with water to 25% solids and 43 g. epichlorohydrin was addedover a period of 15 minutes. This reaction mass was heated to 70° C. andmaintained at this temperature for 5 hours. The final product consistedof 32% by weight solids.

Cationic polymer (3) is a nitrogen-containing polymer obtained bycondensing 1,3-dicyanobenzene with a polyalkylenepolyamine to form a lowmolecular weight polymer. The resulting polymer is then reacted with anepihalohydrin, such as epichlorohydrin. The polyalkylenepolyamine usedin preparing cationic polymer (3) can be a polyethylenepolyamine, apolypropylenepolyamine, a polybutylenepolyamine and the like. Specificexamples of such polyalkylenepolyamines are diethylenetriamine,triethylenetetramine, tetraethylenepentamine, and dipropylenetriamine.

Cationic polymer (3) is prepared in two stages. First,1,3-dicyanobenzene is condensed with a polyalkylene polyamine in a moleratio of 1:1 to provide a condensation prepolymer. This condensationreaction is carried out at a temperature of from 150°-200° C. for aperiod of 1 hour to 4 hours. Time varies inversely with temperature. Thecondensation prepolymer is then reacted, in aqueous media, with anepihalohydrin at elevated temperature, preferably 50° C.-90° C. forabout 1 hour to 4 hours. Time varies inversely with temperature. Onemole of epihalohydrin is used for each mole of amine nitrogen present inthe condensation prepolymer.

EXAMPLE 3

Equipment as used in Example 2 was used in this example. 64 g. (0.5mole) 1,3-dicyanobenzene and 51.5 g (0.5 mole) diethylenetriamine wereadded to the flask to provide a mixture which was heated to atemperature of 165° C. and maintained at this temperature for fourhours. During this time about 0.5 mole of NH₃ was evolved. The reactionproduct was cooled to room temperature (about 23° C.). 23 g. of thereaction product (0.11 amine equivalents) was dissolved in 25 g.methanol, then 75 g. of water was added, followed by 15 g. (0.16 mole)epichlorohydrin, and the reaction mixture was heated to 30° C. andmaintained at this temperature for about 2 hours. The product consistedof 29% by weight solids.

Cationic polymer (4) is a nitrogen-containing polymer obtained by thecondensation of bis-aminopropylpiperazine with an epihalohydrin, such asepichlorohydrin.

Cationic polymer (4) is prepared by the condensation reaction ofbis-aminopropylpiperazine and an epihalohydrin in a mole ratio ofbis-aminopropylpiperazine to epihalohydrin of 1:3 to 1:8, preferably ina 1:4 mole ratio. Reaction is carried out at a temperature of 50°-90° C.until the reaction product has a viscosity, as measured on theGardner-Holdt scale, or F to S. This will usually require a period of 1hour to 4 hours, depending on the temperature employed.

EXAMPLE 4

Apparatus as used in Example 2 was used in this example. 64 g. (0.32mole) of bis-aminopropylpiperazine was mixed with 354 g. water in theflask and 125 g. (1.34 moles) epichlorohydrin was added thereto, slowly,over 15 minutes.

As the epichlorohydrin was added, the temperature of the reaction massrose rapidly to 70° C. and a cooling water bath was applied to maintainthe temperature at 70° C. After the epichlorohydrin addition wascomplete, the cooling bath was removed and the temperature wasmaintained at 70° C. with a heating mantle. The viscosity rose graduallyover an hour and a half to a Gardner-Holdt viscosity of N. The reactionwas quenched by addition of 398 g. water, 6 g. formic acid and externalcooling. The resulting solution had a solids content of 20% and a pH of5.

Acid anhydrides useful as cellulose reactive sizing agents for paper arewell known in the art and include (A) rosin anhydride, see U.S. Pat. No.3,582,464; (B) anhydrides having the structure ##STR1## wherein R₁ is asaturated or unsaturated hydrocarbon radical, the hydrocarbon radicalbeing a straight or branched chain alkyl radical, an aromaticsubstituted alkyl radical, or an alkyl substituted aromatic radical solong as the hydrocarbon radical contains a total of from 11 to 39 carbonatoms; and (C) cyclic dicarboxylic acid anhydrides having the structure##STR2## where R' represents a dimethylene or trimethylene radical andwhere R" is a hydrocarbon radical containing from 8 through 22 carbonatoms which are selected from the group consisting of alkyl, alkenyl,aralkyl or aralkenyl. Substituted cyclic dicarboxylic acid anhydridesfalling within the above formula (II) are substituted succinic andglutaric anhydrides. In formula (I) above each R₁ can be the samehydrocarbon radical or each R₁ can be a different hydrocarbon radical.

Specific examples of anhydrides of formula (I) are myristoyl anhydride;palmitoyl anhydride; oleoyl anhydride; and stearoyl anhydride.

Specific examples of anhydrides of formula (II) are isooctadecenylsuccinic acid anhydride; n-hexadecenyl succinic acid anhydride; octenylsuccinic acid anhydride; and octyl glutaric acid anhydride.

Hydrophobic organic isocyanates used as sizing agents for paper are wellknown in the art. Best results are obtained when the hydrocarbon chainsof the isocyanates contain at least 12 carbon atoms, preferably from 14to 36 carbon atoms. Such isocyanates include rosin isocyanate; dodecylisocyanate; octadecyl isocyanate; tetradecyl isocyanate; 6-ethyldecylisocyanate; 6 phenyldecyl isocyanate; and polyisocyanates such as1,18-octadecyl diisocyanate and 1,12-dodecyl diisocyanate, wherein onelong chain alkyl group serves two isocyanate radicals and impartshydrophobic properties to the molecule as a whole.

Ketene dimers used as cellulose reactive sizing agents are dimers havingthe formula:

    (R'"CH═C═O).sub.2

where R'" is hydrocarbon radical, such as alkyl having at least 8 carbonatoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl andalkaryl. In naming ketene dimers, the radical R'" is named followed by"ketene dimer". Thus, phenyl ketene dimer is: ##STR3## benzyl ketenedimer: ##STR4## and decyl ketene dimer is (C₁₀ H₂₁ --CH═C═O)₂. Examplesof ketene dimers include octyl, decyl, dodecyl, tetradecyl, hexadecyl,octadecyl, eicosyl, docosyl, tetracosyl, phenyl, benzyl, beta-naphthyland cyclohexyl ketene dimers, as well as the ketene dimers prepared frommontanic acid, naphthenic acid, Δ⁹,10 -decylenic acid, Δ⁹,10-dodecylenic acid, palmitoleic acid, oleic acid, ricinoleic acid,linoleic acid, linolenic acid, and eleostearic acid, as well as ketenedimers prepared from naturally occurring mixtures of fatty acids, suchas those mixtures found in coconut oil, babassu oil, palm kernel oil,palm oil, olive oil, peanut oil, rape oil, beef tallow, lard (leaf) andwhale blubber. Mixtures of any of the above-named fatty acids with eachother may also be used.

EXAMPLE 5

An emulsion of a ketene dimer prepared from a mixture of palmitic andstearic acids is prepared by admixing 880 parts of water, 60 parts ofcationic corn starch and 10 parts of sodium lignin sulfonate. Themixture is adjusted to pH of about 3.5 with 98% sulfuric acid. Theresulting mixture is heated at 90°-95° C. for about one hour. Water isthen added to the mixture in an amount sufficient to provide a mixtureof 1750 parts (total weight). About 240 parts of the ketene dimer isstirred into the mixture together with 2.4 parts of thiadiazine. Thethiadiazine is used as a preservative. The resulting premix (at 65° C.)is homogenized in one pass through an homogenizer at 4000 p.s.i. Thehomogenized product is diluted with water to a ketene dimer solidscontent of about 6%.

As is well known in the art, hydrophobic cellulose reactive sizingagents are used in the internal sizing of paper and in the externalsizing of paper. The accelerators of this invention can be used incombination with the sizing agent in either method.

EXAMPLE 6

The products of Example 1 and Example 5 were combined with addition ofwater, as required, to provide an aqueous sizing composition comprisedof 0.10% ketene dimer and 0.10% of the nitrogen-containing polymer ofExample 1.

EXAMPLE 7

The products of Example 2 and Example 5 were combined with addition ofwater, as required, to provide an aqueous sizing composition comprisedof 0.10% ketene dimer and 0.10% of the nitrogen-containing polymer ofExample 2.

EXAMPLE 8

The products of Example 3 and Example 5 were combined with addition ofwater, as required, to provide an aqueous sizing composition comprisedof 0.10% ketene dimer and 0.10% of the nitrogen-containing polymer ofExample 3.

EXAMPLE 9

The products of Example 4 and Example 5 were combined with addition ofwater, as required, to provide an aqueous sizing composition comprisedof 0.10% ketene dimer and 0.10% of the nitrogen-containing polymer ofExample 4.

EXAMPLE 10

An aqueous sizing composition was prepared to provide a sizingcomposition as in Examples 6, 7, 8 and 9 with the exception that as thenitrogen-containing polymer there was employed anaminopolyamide-epichlorohydrin resin. The aminopolyamide was derivedfrom adipic acid and diethylenetriamine. The test results show thiscationic polymer does not function as an accelerator for ketene dimer.

The above sizing compositions are applied to the surface of a sheet of40 lb./3000 ft.² waterleaf paper. The sheet is made from a 50:50hardwood; softwood pulp blend on a pilot paper machine. Each sizingcomposition is adjusted to pH 7 before application to the sheet in thenip of a horizontal size press. The size press runs at 40 ft./min. andthe wet pickup is 70%. Retention of the ketene dimer size is the same inall of these runs. The sized sheets are dried at 93° C. for 20 sec. on alaboratory drum drier to 5% moisture. The sizing is measured by theHercules Size Test with test solution No. 2 to the indicatedreflectance. The off-machine data are obtained within two minutes ofdrying and the natural aged data after 2-5 days storage at roomtemperature. It is known in the art that ketene dimer size developssubstantially all its sizing properties in the paper in 3 days. Afterthis time the size properties of the paper remain essentially the same.The off-machine result is the critical result as it reflects the rate atwhich sizing develops. The surface application of the sizingcompositions eliminates any retention effects of the cationic polymerused.

Size results are set forth in Table I below.

                  TABLE I                                                         ______________________________________                                        Sizing      Hercules Size Test                                                Composition Off-The Machine                                                                             Natural Aged                                        of Example  to 80% Reflectance                                                                          to 85% Reflectance                                  ______________________________________                                        6           127           540                                                 7           26            517                                                 8           15            450                                                 9           165           536                                                 10          0             525                                                 Control     0             450                                                 (ketene                                                                       dimer alone)                                                                  ______________________________________                                    

The above description is illustrative of this invention and not inlimitation thereof.

What I claim and desire to protect by Letters Patent is:
 1. A sizing composition in the form of an aqueous emulsion comprising (A) a hydrophobic cellulose-reactive sizing agent and (B) a sufficient amount of a sizing accelerator of a cationic polymer selected from the group consisting of (1) a cationic polymer obtained by reacting an epihalohydrin with a condensate derived by condensing dicyandiamide or cyanamide with bis-aminopropylpiperazine and (2) a cationic polymer obtained by condensing an epihalohydrin with bis-aminopropylpiperazine.
 2. The sizing composition of claim 1 wherein the sizing agent is a ketene dimer and the cationic polymer is polymer (1).
 3. The sizing composition of claim 2 wherein the epihalohydrin of the cationic polymer (1) is epichlorohydrin.
 4. The sizing composition of claim 1 wherein the sizing agent is a ketene dimer and the cationic polymer is polymer (2).
 5. The sizing composition of claim 4 wherein the epihalohydrin of the cationic polymer (2) is epichlorohydrin. 